DESCRIPTION: (Applicant's Abstract) It is important to develop and evaluate more effective outreach models to engage homeless drug users, who are at risk of contracting and transmitting HIV and other communicable diseases. This study will examine an innovative program, a mobile medical outreach clinic ("medical van") which provides primary medical care and medical referrals for homeless clients with high rates of substance abuse and HIV risk behaviors. The study will experimentally enhance the medical van with Intensive Case Management that will provide comprehensive psychosocial assessment and referrals with follow-up for substance abuse treatment, mental health care, housing assistance and other social services. The specific aims are: 1. Conduct a medical, drug treatment and social needs assessment survey of homeless visitors to an existing medical van, including medical conditions and infections (tests for HIV, TB, hepatitis-B and C, syphilis); drug/alcohol use and sexual behaviors (related to HIV); mental health needs; housing and other social service needs. 2. Conduct a process evaluation of the medical van which serves homeless drug users at various sites (e.g., shelters, meal programs) in New York City. 3. Conduct an outcome evaluation of the medical van with Intensive Case Management as an experimental enhancement. 4. Examine gender differences in service processes and client outcomes for the medical van and the case management intervention. Representative samples of homeless adult male (N=150) and female (N=150) medical van visitors will be randomly assigned to: (a) medical van plus Intensive Case Management or (b) medical van service "as usual." All subjects will be interviewed at baseline and followed-up at 6 months; hair and urine specimens will be collected to determine substance use. At baseline all subjects will be tested for HIV, hepatitis (B and C), TB and syphilis. Primary outcomes to be examined are: receipt of appropriate medical treatment, service referral outcomes, improvement in physical and mental health, entry to and retention in substance abuse treatment, reduction of drug/alcohol use and HIV risk behaviors.